Clutch



2 Sheets-Sheet l INVENTOR.

ATTORNEYS.

July 24, 1934- R. c. RUSSELL CLUTCH Filed Aug. 21 1935 July 24, 1934. RRUSSELL 1,967,563

CLUTCH Filed Aug. 21. 193s 2 sheets-sheet 2 INVENTOR. 'oer C. z/Sserl ATTRNEYS UNITED STATES PATENT OFFICE CLUTCH Robert C. Russell, Detroit,Mich.

Application August 21, 1933, Serial No. 686,019 13 claims. (o1. 19a-36)vThis invention relates to clutches and particularly to clutches of theplate type, the principal object being the provision of a. clutch whichmay be operated with a minimum expenditure ofenergy on the part of theoperator.

Other objects include the'provision oi a servo mechanism for effectingdisengagement of a clutch; the provision of a clutch in which powerderived from the drivingmember may be employed for moving the clutch toreleased position;

the provision of a clutch having spring means normally urging it towardengaged position and friction means under the control o f the operatorof the clutch enabling the operator to tap the power in the drivingoperation of moving the clutch to member and apply it to the releasedposition; and the provision of a clutch having a servo mechanismassociated therewith so constructed and arranged that the operationeither to or from engaged position of the clutch is at all times underabsolute control of the-operator whether the driven member is rotatingor not, including a pilot or auxiliary friction device both members ofwhich are'bodily movable and one of which is under the control of theoperator.

Other objects include having a pair of members normally the provision ofa clutch rotatable with 'the driving member thereof, one of said pair ofmembers being so related with respect to the other thereof that relativerotation between them causes axial movement of one relative to theother, and manually controllable friction means associated and bodilymovable with the axially movable one of said pair of members whereby therotation thereofvrelative to the other may be retarded in a controlledmanner. thereby to movement of the clutch through cause desired relativeaxial movement between said pair of members; the provision of a plateclutch having a for equal rotation with the member fixed driving elementof the clutch and a second member normally rotatable with but alsorotatable relative tothe first member, anti-friction means beinginterposed between said members and the membersbeing so formed that uponrelative rotation between them axial movement is imparted to one ofthem,

and

manuallycontrollable means frictionally associated with one of saidmembers whereby to enable retardation of its rotation r other andthrough relative tween the members cause disengagement clutch.

Other objects include the provis type of clutch having anism to effectdisengagement th elative to the axial movement beof the ion of a plate anovel form of servo mech-l ereof and including a pair of associatedrings, one of which is fixed for equal rotation with the driving memberof the clutch, and the rings being provided with complementary inclinedsurfaces at their adjacent ends, anti-friction means being providedbetween the complementary inclined surfaces and means being provided foreffecting relative rotation between the rings whereby to cause axialdisplacement of one with respect to the other; the provision of amechanism as above described in which the inclined teeth are so shapedas to cooperate with the antifriction means to limit a relative rotationbetween the rings; the provision of a mechanism as abovedescribed inwhich the inclined surfaces are in the form of threads; and theprovision of a mechanism of the type descr bed in which a novel means isprovided for maintaining the relative position of the balls with respectto each other and to the rings.

Otherobjects include the provision of a novel servo lmechanism forclutches including a pair of relatively rotatable members havingconi'p'lementary inclined teeth, the teeth being inclined at varyingdegrees between their' end surfaces whereby to enable the desired degreeof axial movement to be obtained between them while. permitting them tobe maintained in axially displaced relation with a minimum of effort.

Other objects include the provision of a novel servo mechanism foroperating a clutch so designed as to permit actuation of theclutchmanually without the aid of the servo mechanism.

Further objects include the provision of a plate type of clutch havingspring means for indirectly clamping the clutch elements togetherincluding co-acting cam elements constantly urged toward one dlrectionof rotation withrespect to each other, and means frictionally associatedwith one of the cam elements capable of being actuated to cause relativerotation between the members in a direction opposite to that in whichthey are normally urged, thereby to effect release of the clutch.

The above being among the objectsof the present invention the sameconsists in certain novel features of construction and combinations ofparts to be hereinafter described with reference to the accompanyingdrawings, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate suitable'embodiments ofthe present invention and in which like numerals refer to ,like partsthroughout the several different views,

Fig. 1 is a partially broken, partially secrings and cooperating ballmembers in a position in which the rings are separated a maximum amount.

Fig. 5 is a fragmentary, partially sectioned, side elevational View ofthe servo mechanism for the clutch shownin Fig. 1 illustrating theposition of the parts thereof when the clutch is disengaged solely bymanual pressure.

Fig. 6 is a fragmentary, partially broken, vertical sectional view takenaxially through a modified form of servo mechanism for the clutch shownin the previous views.

Fig. '7 is a transverse vertical sectional view taken on the line 7--7of Fig. 6.

Fig. 8 is a vertical sectional view taken longitudinally through amodified form of clutch construct-ion.

Fig. 9 is a vertical, transverse sectional view` taken on the line 9 9of Fig. 8.

While the present invention is applicable to clutches regardless oftheir use, as will be readily understood by those skilled in the art, itis particularly adaptable for use in connection with motor vehicles andfor that reason and for the purpose of illustrating one suitable useonly its application to motor vehicles will be referred to herein.

As is well understood by those skilled in the motor vehicle art, thepresent trend of design is toward more powerful engines, and reducedoverall height of the vehicle which means decreased ground clearance.The increased power of the vehicle demands a clutch capable of handlingan increased load and the reduced ground clearance demands a clutch ofminimum diameter which inturn requires higher clutch pressures.

' Where such a clutch is released purely through manual pressure as inthe majority of conventional constructions, and due to the limitedamount of permissible pedal travel for the clutch operating lever, it isobvious that the pedal pressure required to operate the clutch becomesexceedingly large, in fact so great that in many structures now on themarket it becomes exceedingly tiresome to the operator where he isrequired to continuously operate the clutch. At the same time, not onlyis it'tiresome to operate clutches requiring a heavy pedal pressure butsuch pressure detracts from the desired accuracy of .control which isnecessary in most cases to obtain a smooth clutch action.

Recently attempts have been made to overcome the disadvantage, of themanual operation of clutches requiring high pedal pressures by theemployment of a vacuum cylinder connected with the intake manifold ofthe engine driving the vehicle and, while this eliminates the necessityof the vehicle operator from exertion in disengaging the clutch, themechanism is necessarily so constructed that the operator has little, ifany, actual control of the engaging movements of the clutch, whichbrings about an undesirable condition particularly in view of the factthat clutch engagement requirement at one speed position of thetransmission is necessarily different from that at another speedposition of the transmission.

In accordance with the present invention a construction is .providedwherein, regardless of the actual amount of force necessary to separatethe driving and driven elements of the clutch, the vehicle operator mayeffect either engagement or disengagement of the clutch through a footpedal without requiring the expenditure of more than a nominal amount ofenergy on his part, and at, the same time movements of the clutch partsat all,times are absolutelyl under control of the drivel` in such amanner that the clutch may either b'e disengaged or engaged at anydesired rate, according to his wishes. In attaining this result power tooperate the clutch is derived from the driving member of the clutchwhich of course is directly connected to the vehicle engine, through theemployment of an auxiliary or pilot clutch-like apparatus which requiresa minimum amount of energy for its operation.

Referring now to the drawings, and particularly to Figs. 1 to 4inclusive, an engine crank shaft is indicated at 10 having a flange 12formed on its rear end which is secured to the web 14 of a flywheelhaving a rim 16. The clutch housing surrounding the flywheel isindicated at 18 to the rear face of which is secured as by means of capscrews'` 20 the bell housing portion 22 of a transmission casing 24.Rotatably mounted in the front wall 26 of the transmission casing 24 isa shaft 28 which projects forwardly therefrom and its forwardly reducedend is rotatably supported by a bearing 30 mounted within the rear endof the crank shaft l0 in a conventional manner. Immediately rearwardlyof the flange l2 of the crank shaft 10 the shaft 28 issplined as at 32and ,slidably but non-rotatably received thereon is the hub 34 of aclutch driven member 36 provided on opposite faces with a suitablefriction material 38 in accordance with conventional practice. Securedto the rear face of the rim 16 of the flywheel as by cap screws 40 is aclutch cover 42, shown as being formed from sheet metal, and extendingfirst radially inwardly of the rim 16 of the flywheel, thenapprovimately axially in a rearward direction as at 44, and then againradially inwardly as at 46. A pressure plate 48 of ringlike formation islocated between the cover 42 and the clutch driven element 36 and aplurality of coil springs 50 constantly maintained under compressionbetween the wall 46 of the clutch cover 42 and the pre'ssure plate 48constantly urge the pressure plate 48 toward the web 14 of ,the flywheelso as to clamp the driven disc 3,6

therebetween for equal rotation therewith. Suitable means, not shown,connect the pressure plate 48 to the flywheel for equal rotation there#with but permit relative axial movement between them in accordance withconventional practice.

A plurality of axially parallel rearwardly projecting studs 52 arethreaded into the pressure plate 48 adjacent the outer edge thereof andproject through the radially extending outer portion f of the clutchcover 42. A radially extending clutch finger 54 is slidably receivedadjacent its outer end upon each of the studs 42 and projects radiallyinwardly therefrom through an opening 56 in the portion 44 f the clutchcover 42 and into a position where its inner end may be readily engagedby the clutch throwout or thrust bearing 58. An abutment for each of thefingers 54 is provided on the corresponding stud 52 in the form of anadjustable nut 60, and a coil spring 62 surrounding each stud 52 ismaintained under compression between the corresponding finger 54 and'thepressure plate 48 to maintain the finger lof plate-like form. Assumingagainst the abutment and to aid in preventing rattling thereof. Anotherrelatively light coil spring 64 is provided between each finger 54 andthe rear wall 46 of the clutch cover 42 to further aid in preventingrattling of the fingers 54 during operationof the clutch.

The construction thus far described is entirely conventional and as faras the present invention is concerned, any other similar conventionalconstruction may be employed in its place.

In accordance with the present invention a 'i member 66 is fixed to thepressure platel48 as by means of screws 68 and is providedIv witharearwardly extending sleeve '70 concentric with the shaft 28 andpreferably radially spaced therefrom as indicated. The bearing 58 isshown in the present vcase as being rotatably and slidably mounted uponthis sleeve '70. Relatively non-'- rotatably but axially slidablymounted on and adjacent the rear end of the sleeve '70 and maintainedagainst rearward movement thereon by means of a nut 72 which may also beemployed for compensating for wear of the clutch facings 38, is a member'74 in the form of a ring, the axially forward face of which is providedwith a plurality of equally angularly arranged axially inclined surfacescr teeth '76, two of such teeth being shown as preferably, although moremay be used in some cases. Another ring member '78 is rotatably andaxially slidably mounted on the sleeve I'70 forwardlyv of the ring '74and its rear axial face is provided with two equally angularly spacedinclined surfaces or teeth complementary in inclination and angularextent to the teeth 76. Suitable anti-friction means, illustrated as aplurality of bearing balls 82, are interposed between cpposed teeth '76and 80 and are maintained in equally angularly spaced relation about theaxis of the shaft 28 by a retainer 83 that -the clutch turns in theconventional direction, that is, in a yclockwise direction as viewedfrom the right hand end of Fig. 1, then the teeth '76 and 80 areinclined in a direction corresponding to that of a right hand thread,and where the bottom of one tooth joins the top of the adjacent tooththe rings '74 and '78 are radiused as at 85 an amount corresponding tothe curvature of the balls 82 so as to form a reverse movement stoptherefor as will hereinafter be more fully brought out.

To the forward face of themember '78 is fixed a disc 84, bodily movabletherewith, in the present case shown as an integral part of the rearelement of the thrust bearing 58,-'having a ring 86 of friction materialsecured to its rear face as by means of rivets 88.

A member 90 suitably fixed to the forward face of the transmission frontwall 26 is provided with a forwardly projecting sleeve portion 92concentric with the axis of the shaft 28 and upon which is slidablyreceived a sleeve 94 provided at its forward end with a radiallyoutwardly extending flange 96, the forward face of which is formed andadapted for engagement with the friction ring 86. Suitably supportedwithin the bell housing 22. is the usual clutch shaft 98 provided withthe usual yoke 100 the free ends of which engage in diametricallyopposite pockets 102 formed on the sleeve 94. Exteriorly of the bellhousing 22 a clutch pedal 104 of conventional construction is secured tothe shaft 98.

Assuming that various parts of the clutch are in the position indicated'in Fig, 1, it will be apparent that the clutch is engaged so that anypower being exerted by the crank shaft 10 will (be directly transmittedthrough the shaft 28. Assuming now that the clutch is turning in thedirection previously noted and the parts are in the position indicatedin Fig. 1, the flywheel, pressure plate 48 and driven disc 36will allrotate in the same direction at equal velocities and, because the ringmember '74 is fixed for equal rotation with the pressure plate 48, itwill also turn therewith. Although theI ring member '78 is free torotate relative to the axis of the sleeve '70, the ends of the fingers54 in pressing rearwardly against the thrust bearing 58 will urge thering member '78 rearwardly and tend to rotate the member '78 in adirection so as to reduce the combined axial dimensions of the rings '74and 78 to a minmum as indicated in Fig. 1 and, accordingly, the ring '78will also tend to rotate with the ring '74 and the remaining parts cfthe clutch.

If now it is desired to disengage the clutch the upper end of the clutchpedal 104 is pressed forwardly causing the shaft 98 to be rocked in aclockwise direction as viewed in Fig. 1 and causing the free ends of theyoke to urge the sleeve 94 forwardly and bring the forward face of itsflange 96 into contact with the friction ring 86 secured to the disc 84.When this occurs the friction set up between the flange 96 and the ring86 will tend to retard the rotation of the disc 84 and consequently thering '78 relative to the ring '74, and when such retardation occurs theballs 82 will roll toward the respective points of the cooperating teeth'76 and 80 and thus force the ring members 74 and '78 axially away fromeachother towards the position indicated in Fig. 4. Thel ring '74 beingmaintained against axial rearward displacement, the ring '7 8 will moveforwardly with the thrust bearing 58 and cause the latter to pressagainst the inner ends of the clutch fingers 54 and cause such fingers54 to pivot about the forward edge of their respective openings 56 inthe clutch cover 42, and this movement of the fingers 54 acting throughthe nuts 60 and studs 52 will tend to cause.' the pressure plate 48 tobe withdrawn rearwardly against the force of the springs 50 so as tofree the clutch driven disc 36 between, it and the web 14 of theflywheel, thus disengaging the clutch.

Obviously, if the pedal 104 is depressed only far enough to permit aninitial engagement of the flange 96 of the sleeve 94 with the frictionring 86 on the disc 84, and then is held in such position` only initialrotational movement of the ring '78 relative to the ring 74 will occurfor, as soon as such partial rotation of the ring '78 occurs, it willdraw away from the flange 96 so as to relieve the friction between itand the flange 96, and as soon as such friction is relieved suicientlyto permit equal rotation of the rings '74 and 78, no further relativerotation of the ring 78 will occur. This partial relative rotation ofthe ring 78 may not be sufficient to cause release of the clutch, but iffurther releasing movement of the clutch is desired all that isnecessary is to press the clutch pedal 104 a further-amount to again setup sufficient friction between the flange 96 and friction disc 86 tocause a further relative rotation between the rings '74 and '78.Obviously` if the pedal 104 is depressed and continued pressure isapplied thereto so as to cause the ange 96 to follow up forward movementof the friction ring 86 in moving forward with the ring '78, continuedrelative rotation of the ring '78 will occur until thc clutch is movedto fully disengaged position. In

other words, to cause complete disengagement of the clutch the pedal 104must be depressed sufliciently to bring the flange 96 on the sleeve 94into contact with the friction ring 86 which is xed to the ring 78 andthe movement of the pedal 104 must continue to follow up the actualdisplacement of the ring 78. Conversely, when the clutch is fullyreleased and it is desired to re-engage it, the amount of re-engag'ementmay be easily and accurately controlled by the amount which the clutchpedal 104 is allowed to return toward normal position, and because ofthis fact it will be obvious that the pedal 104'may be so controlled bythe operator that any amount or degree of slippage of the clutch may becaused to occur during engagement thereof, thus permitting the desiredsmooth acceleration of the vehicle in which the clutch is mounted,through proper controlled slippage of the clutch,

It may be noted that suiricient relative rotation of the ring 78 topermit the balls to roll over the high ends of the teeth 76 and 80 maybe prevented in any suitable manner, for instance, as by providing astop for the pedal 104 to prevent it from being moved through a distancewhich would be sulicient to cause the balls 82 to roll over the ends ofthe teeth. Such a stop may take the form of adjustable means supportedeither by the clutch housing 18 or bell housing 22 but, for the purposeof simplicity, it may be considered that the floor board 106 contactingwith the pedal pad 108 of the pedal 104 will serve the desired purposeand thus will limit the movement of the ring 78 so as to prevent theballs 82 from rolling beyond the position indicated in Fig. 4. The rings74 and 78 are, of course, limited lin their relative rotation in theopposite direction by the balls 82 seating in the radiused surfaces 85of the opposed members. It may also be noted that when the pedal pad 108contacts with the floor board 106 so as to move the rings 74 and 78 tothe relative positions indicated in Fig. 4, the ange 96 and frictionring 86 will simply slip relative to one another Without causing anyadded relative rotation of the ring 78 when the clutch is in fullydisengaged position. v

The amount of pressure which it is necessary to apply manually to thepedal 104 to retard theV rotation of the ring 78 and to move the clutchto disengaged position, will vary in accordance with the diameter of thedisc 84 and the inclination of the teeth 80. r1`he diameter of the disc84, for the purpose of oompactness in arrangement of the clutch, ispreferably kept at a minimum, and it will be recognized that theinclination of the teeth 76 and 80 must be such as to insure a completedisengagement of the clutch and at the same time be'suflicient to takecare of normal wear of the clutch facing 38.

With the construction of the rings 74 and 78 shown it will be noted thateach of the teeth-76 and extends through approximately 18D degrees ofangularity and that, in order to move the balls 82 from simultaneouscontact with the radiused portions on both rings to a position adjacentthe tip of cooperating teeth 76 and 80, the ring 78 must rotate relativeto the ring 74 through an angle of approximately 360 degrees. It will berecognized that if the teeth 76 and 80 contacted directly togetherWithout the interposition of rolling anti-friction means, then themaximum rotation of the ring 78 with respect to the ring 74 would belimited to the length of the teeth, that is, in the present casesubstantially-180 degrees, the maximum axial displacement would belimited it will be noted that the balls 82 are seated at the opposedbasesof the teeth 76 and 80 when the rings are in a position of minimumcombined axial length, and that when the ring 78 rotates. relative tothe ring 74 the balls 82 roll circumferentially of the rings at half therelative speed of their track on the ring '78. 'I'he yresult of this isa differential action set up between the rings 74 and 78 and the balls82 such that the ring 78 must turn twice the length ot the teeth 80 inorder to make the balls 82 roll the length of the teeth 76, the balls 82rolling along the teeth 80 at half apparent that the required axialdisplacement between the rings 74 and 78 is obtained with but half ofthe force which would be required to retard rotation of the ring 78in acase where the balls 82 were omitted and the teeth allowed to slidedirectly on one another, this being true because the force may actthrough twice the distance to perform the required work. This amount ofrelative angular movement between the rings 74 and 78 permits theangularity of the teeth 76 and 80 to be such that a relatively smallpressure between the ilange 96 and friction member 86, and also on thepedal 104, is suillcient to fully disengage the clutch, and this isparticularly true in a smaller type of clutch.

This light pressure on the pedal 104 will, in

many cases, induce the operator of the vehicle to hold the clutch out ofengagement to permit the car to coast without driving `the engine, in

other words, to free Wheel. It will be apparent that such practice onthe part of the operator will mean that the ange 96 and ring 86 arebeing pressed together and continually slipping relative to each other,but that suflicient friction is being set up between them to maintainthe clutch disengaged. In the lighter types of clutches this frictionmay not be great enough to result in undue heating of the ring 86 andflange 96 under such circumstances, but in the heavier sizes of clutchesthe pressure required to hold the clutch may be great enough to causesufficient pressure on the ring'86 to burn it up. For this reason it isextremely important that the inclination of the teeth 76 and 80 be assmall as possible so that the pressure required to be exerted betweenthe iiange 96 and ring 86 to hold the clutch in disengaged position willbe correspondingly lowV as will be the frictionset up between the flange96 and ring 86. At the same time, however, the inclination of the teeth76 and 80 must be great enough to impart sufficient axial movement tothe ring 78 to cause complete disengagement of the clutch even after anormal amount of Wear of the friction rings.

I have found it essential, particularly in the larger clutches, to,employ not more than two teeth on each of the rings 74 and 78, thuspermitting a substantially full turn of the ring 78 in moving the clutchto disengaged position. While this permits a material reduction in theinclination of the teeth 76 and 80 over anything heretofore proposed, Ifind it desirable to accentuate this reduction of inclination for clutchreleased position of the ring 78, that is, where the inclination iseffective in holding the clutch fully released as in using the clutch tofree wheel", by further modifying the construction as indicated best inFig. 3 in which it is shown applied to the ring 78 only, it beingunderstood that the ring '74 is similarly formed.

Referring to Fig. 3 it will be noted that the inclination of. each tooth80 is relatively great adjacent the corresponding radius 85, and thatthe inclination of each tooth gradually decreases up to a point asubstantially midway its length, and from such point a to the tip of thetooth the inclination remains substantially constant at a relativelysmall value. With this construction the majority or even all of theaxial movement of the ring 78 may be obtained after a partial rotationalmovement only thereof, and after the balls 82 have reached the lowinclined outer ends of the teeth the ring 78 may be maintained in thisposition with an exceedingly small amount of pressure exerted betweenthe flange 96 and ring 86 with correspondingly small amount of frictionbetween them to cause heating thereof. By this means possibility ofburning up the ring 86 is effectively prevented but the pressure on thepedal 104 necessary to hold the clutch disengaged is also reduced and insome cases to such an extent that in order to obtain 'the proper feel ofthe clutch it is desirable to employ a spring such as 203 to constantlyurge the pedal 104 toward clutch engaged position.

It will be recognized by those skilled in the art that the abovedetails, while they may appear -more or less trivial to those notskilled in the art are, in reality, features that materially aid inmaking the clutch a commercially practicable structure.

In exceptionallyV large and heavy clutches such as may be found on thelarger sizes of trucks and busses, even the expediente outlined abovemay be found insufficient for reducing the pressure required between theflange 96 and ring 86 to continuously hold the clutch in disengagedrelation without danger of undue heating of the ring 86, and in suchcases it may be necessary to modify the above described construction inthe manner indicated in Figs. 6 and 7.

i Referring to Figs. Sand 7 it will beA noted that the member 66 in Fig.1 has been replaced by a member 66' in the center of which is suitablyfixed a rearwardly extending elongated ring member or sleeve 70 theouter surface of which is formed with a right hand thread 108 ofsemi-circular cross section; Surrounding the sleeve 70' is another ringmember or sleeve 110, slightly shorter than theA sleeve '70', and theinner surface of which is provided with threads 112 opposed to thethreads 108. A plurality of bearing balls 114 are arranged between theopposed threads 108 'and 112 and are maintained in their proper spacedreflange 118 to which the disc 84 is secured for equal lation by meansof a retainer sleeve 116. 'Ihe outer sleeve 110 is provided with aperipheral rotation by means of pins 119 fixed to the disc 84 andaxially slidably received in the flange 118 in the same relation to theflange 96 on the member 94 as in the previously described construction.l

With this construction it will be apparent that when the pedal 104 isdepressed sufficiently to bring the flange 96 into contact with thefriction ring 86 the rotation of the outer sleeve 110 with the drivingmember of the clutch will be retarded and relative rotation will occurbetween the sleeve 70' and 110 which will cause the outer sleeve 110 tomove to the right, as viewed in Fig. 6, and urge the clutch lingers 54toward clutch disengaged position, and that if the forward, movement ofthe pedal 104 is continued so as to cause the flange 96 to continue tofollow the forward movement of the friction ring 86 with the outersleeve 110, that the clutch will be completely disengaged. Thefunctioning of the sleeve 70 and 110 with the intervening balls 114 willthus be. equivalent to the construction previously described. There isthis difference however, that where the previously describedconstruction is limited to an angular displacement of the ring 78 withrespect to the ring 74 of substantially 360 degrees, in the constructionillustrated in Fig. 6 the sleeve 110 may move through two or morecomplete turns. This not only permits the pitch of the threads, whichcorresponds to the inclination of the teeth 76 and 80 in the previouslydescribed construction, to be materially reduced so as to lower thepressure required between the flange 96 and ring 86 to operate theclutch, but also permits a greater movement of the free ends of theclutch fingers 54 in order to move the clutch to disengaged position.

In order to insure maintenance of the balls 114 in their properoperative relationship, inner sleeve 70' is provided at its rearward endwith an outwardly projecting circumferential flange 120, and the rearend of the retainer 116 is outwardly flared to provide a flange 122. Theflange 120 and the rear end of the sleeve 110 thus act as stops for theflange 122, and the position of the sleeve 116 and the balls 114embraced thereby is thereby controlled so that in all cases when theclutch is operated to cause forward movement of the outer sleeve 110,free rolling of the balls 114 in their respective grooves will beassured. This is for the reason that the balls 114, during movement ofthe sleeve 110 relative to the sleeve 70 will normally tend to moveaxially at half of the axial speed of the sleeve 110, so that when thesleeve 110 is moving forwardly away from the flange 122 there can be nopossibility of anything interfering with the free rolling of the balls114. Furthermore, when the sleeve 110 is moving forwardly, the load onthe balls will force them to roll in their grooves. When the clutch isin engaged position there will be no load on the balls 114 andconsequently the retainer sleeve 116 and balls 114 may become slightlydisplaced from the position shown due to vibrations to which the clutchis subjected or from other reasons, but the flange 122 cooperating withyeffect operation of the clutch. Occasions may arise wherein it isdesirable to be able to release the clutch when it is not rotating. Thismay be accomplished in the structures shown in Figs. 1 to 7 inclusive bysimply pressing down the pedal 104 which, acting through the sleeve 94and flange 96, will move the disc 84 and'thrust bearing l58 forwardlyagainstthe inner ends of the clutch fingers 54 to release the clutch.`In the construction shown in Figs. 6 and l the disc 84 inmovingforwardly simply slides the pins 119 in their openings in thefiange 118 without disturbing the position of the sleeve 110.

In the construction illustrated in Figs. 1 to 5 inclusive it will beapparent that the disc 84 in moving forwardly solely under the influenceof axial pressure from the sleeve 94 will carry with it the forward ring78 which is secured to the disc 84, and unless otherwise prevented thering 78 in moving forwardly with the disc 84 would pull away from thering 74 and leave the balls 82 free to move between them. In such casethe balls 82 might become displaced circumferentially of the teeth 76and 80 with the result that when the pedal 104 is allowed to return tonormal position the balls 82 might prevent proper return movement .ofthe ring 78 to fully retracted position, and .thereby interfere with theproper engagement of the clutch. As best indicated in Fig. 5, to guardagainst such possibility, a spring member in the form of a ring 71 isinterposed between the nut 72 and the ring 74, the ring 71 beingprovided with a plurality of circumferentially extending spring fingers73 which are bent laterally out of the plane of the ring 71. 'Ihesefingers exerta relatively light pressure tending4 to separate the nut 72and ring 74 and normally are sprung into the plane of the ring 71through the pressure of the clutch lingers 54 acting through the'thrustbearing 58 and intervening parts, but in case where the ring 78 is movedforwardly solely by axial pressure exerted through lthe sleeve 94 thefingers 73 cause the ring 74 to follow the movement of the ring 78forwardly, as indicated in Fig. 5, and thus hold the balls 82 betweenthe rings 74 and 78 and prevent them from becoming displaced.

In Figs. 8 and 9 a modifledform of structure is 'illustrated by means ofwhich a result equivalent to that obtained in the foregoing constructionis obtained with a considerably less number of parts. Referring to thesefigures it will be noted that an engine crankshaft 130 has secured toits rear end a flywheel including a web 132 and rim 134. A clutch shaft136 has its reduced forward end suitably journaledY in a bearing 138secured in a recess 140 in the rear end' of the crank shaft 130 andrearwardly thereof is splined as at 142 for non-rotatably butA axiallyslidably receiving the hub 144 of the clutch driven disc 146 providedwith friction facings 148 on its'opposite faces. A clutch-cover `150 issecured to the rear edge of the flywheel rim 134 by cap screws 152 andbetween the cover 150 and the clutch driven disc 146 is a pressure plate154 which is maintained in concentric relation with respect to theclutch and supported therein for limited axial movement by spring strapsor links 156 each of which is secured at one end to the pressure plate154 by cap screws 158 l and at their opposite ends to the clutchcover150 by bolts 1 60. These straps or links 156 form the subject matter'ofmy copending application for Letters Patent of the United States forimprovey ments in clutches, filed August 5, 1933, Serial No. 683,719,and are fully disclosed therein. Preferably they are so tensioned as toconstantly urge the `pressure plate 154 towards clutch disengagedposition. It is to be particularly noted that no packing Asprings orclutch fingers, such as the springs and fingers 54 in Fig. 1 and theirassociated parts, are provided in'this construction.

The clutch cover 150 and pressure plate 154 are provided with centralbushings 162 and 164 respectively'in which is axialy slidably received asleeve member 166 on the rear end of which is wardly of the ring 172 aring 176'is fixed upon the sleeve 166 and this ring may be consideredidentical in all respects to the ring 78previously described and ashaving inclined teeth 178 corresponding to the teeth 80 on the ring 70.Balls 180 are disposed between the opposed teeth 174 and 178 and aremaintained in operative position by' means of a retainer ring 182. Athrust bearing 184 is provided between the central portion of thepressureplate 154 and the forward face of the ring 176. A helical spring188 has its inner end fixed to the periphery of the ring 176 as at 189in Fig. 8 and its outer end is formed into an eye 190 in which isreceivd a stud 192 fixed to the clutch cover 150 by means of a nut 194.Considering the clutch to turn in the conventional direction, the turnsofthe spring 188 extend in a clockwise direction as viewed in Fig. 9 andas traced in a direction from the outer end of the spring toward theinner end thereof.

^ 'I'he disc member 168 is provided on its forward face with a ring 196of friction material, and positioned forwardly in advance of the disc168 and normaly out ofr contact with the friction ring 196 is a ringmember 198 the rear face of .which is formed for interengagement withthe friction disc 196, and provided on diametrically opposite sides withradially projecting pins 200 adapted for engagement with. the arms .of ayoke 202 corresponding to the yoke arms 100 previously described inconnection with Fig. 1 but adapted to be operated in a rearwarddirection Aupon depression of the usual clutch pedal correring 176 in aclockwise direction as viewed from the front or the right hand end asviewed in Fig. 8, and this tends to rotatethe ring A176 in a clockwisedirection relative to the ring 172 as viewed from the right hand end ofFig. 8 so as to cause axial displacement between the rings 172 and 176,urging the ring 176 forwardly and, acting through the thrust bearing184, forces the pressure plate 154 forwardly so as to clamp the drivendisc 146 between it and the web 132 of the flywheel. Consequently, thespring 188 in acting through ythe ring 176 constantly urges the' clutchtoward engaged position and maintains it inengaged position except vwhenotherwise controlled. Considering the clutch to be in the positionindicated in Fig. 8, it will be observed that if the ring 198 is movedrearwardly so as to cause it to engage the friction ring 196, thefriction ring 196 will be retarded in its rotation and will cause a likeretarding in the rotation of the ring 176. This will cause a relativerotation of the ring 176 in a counter-clockwise direction as viewed fromthe right hand end of Fig. 8 and will cause the balls 180 to roll towardthe bottom of the teeth.

manipulation of the clutch pedal the action of this clutch maybecontrolled in substantially identical manner as the clutch previouslydescribed may be controlled. It will be observed that in releasing thisclutch the ring 198 and consequently the foot pedal controlling it willhave to follow the rearward movement of the disc 168 and ring 176 tocontinue the releasing move- -ment of the clutch in a manner equivalentto that of the construction previously described.

In order to guard against possible displacement of the spring 188 underthe influence of the centrifugal force which the spring is subjected toduring rotation of the clutch, it may be desirable to provide means inthe form of abutments for the spring in order to maintain it in itsproper position. Such means may take the form of stop pins 204 suitablyfixed in the clutch cover 150 and positioned in approximate contact withthe outer turn of thespring 188 adjacent its free end as illustrated inFig. 9.

In both of the above described mechanisms it will be apparent that thepressure which it is necessary to manually apply to the clutch pedal inorder to bring the braking surfaces of the cam rings into sufficientengagement to cause actuation of the cam rings, is relatively small andbut a small percentage of the pressure which it is necessary to apply inmanually controlled clutches of conventional construction, and that atthe same time by the means provided it is possible to control the clutchjust as precisely and accurately as such conventional clutches may becontrolled by the foot in ordinary practice.

Formal changes may be made in the specific embodiments of the inventiondescribed Without departing from the spirit or substance of the broadinvention, the scope of which is commensurate with the appended claims.

I- claim:

1. In a clutch structure, in combination, a driving element, a drivenelement, a pressure plate adapted to clamp said driven element to saiddriving element, spring means constantly urging said pressure platetoward said clamping position, a member driven directlyby said drivingelement, a second member relatively rotatable with respect to the rstmentioned member, said members being so formed and so cooperating witheach other that relative rotation between them effects axial advancementof said second member relative to the first mentioned member, meansoperatively connecting said second member and said pressure plate forcorrelated movements, a part axially and rotatably movable with saidsecond member, a second non-rotatable part movable axially of ,saidclutch and arranged for frictional engagement with the rst mentionedpart, and

means for controlling the axial position of said -second part.

2. Ina clutch structure, in combination, a driving element, a drivenelement, a pressure plate adapted to clamp said driven element to saiddriving element, spring means constantly urging said pressure platetoward said clamping position,

a member driven directly by said driving element,

a second member relatively rotatable with respect to the rst mentionedmember, said members being so formed and so` cooperating with each otherthat relative rotation between them effects axial advancement of saidsecor. member relative to the first mentioned member, means operativelyconnecting said second member and said pressure plate for correlatedmovements, a part axially and rotatably movable with said second member,a second non-rotatable part movable axially of said clutch and arrangedfor frictional engagement with the first mentioned part, and means formoving said second part into Contact with the first mentioned partwhereby to retard the rotation of said second member relative to the rstmentioned member and effect an axial displacement of said pressureplate, said means being operable to move said second part axially withthe first mentioned part as said second member advances to release saidpressure plate whereby to prevent frictional disengagement of said partsdue to the advancement of said second member.

3. In a clutch structure, in combination, a driving element, a drivenelement, a pressure plate adapted to clamp said driven element'to saiddriving element, spring means constantly urging said pressure platetoward said clamping position, a member rotatable with said drivingelement, a second member relatively rotatable with respect to the firstmentioned member, said members being so formed and so cooperating witheach other that relative rotation between them effects axial advancementof said second member relative to the first mentioned member, meansoperatively connecting said second member and said pressure plate forcorrelated movements, a part fixed for equal rotation with said Ysecondmember but axially movable relative to or simultaneously therewith, asecond non-rotatable part movable axially of said clutch and arrangedfor frictional engagement with the first mentioned part, and means forcontrolling the axial position of said second part.

4. In a clutch structure, in combination, a driving element, a drivenelement, a pressure plate, spring means constantly urging said pressureplate toward a position to clamp said driven element to said drivingelement, means for retracting said pressure plate against the force ofsaid spring means including a pair of telescoping sleeves one of whichis constantly rotatable with said driving element and the other of whichis both rotatable and axially movable with respect to the rst mentionedsleeve, said sleeves having opposed thread-like grooves formed in theiropposed faces, anti-friction means received in said opposed grooves,means for effecting a relative rotation of said other of said sleevesduring rotation of said driving element, and means operativelyconnecting said other of said sleeves with said pressure plate.

5. In a clutch structure, in combination, a driving element, a drivenelement, a pressure plate,

spring means constantly urging said pressure plate toward a position toclamp said driven element to said driving element, means for retractingsaid pressure plate against the force of said spring means including apair of telescoping sleeves one of which is driven directly by saiddriving element and the other of which is both rotatable and axiallymovable with respect to the rst mentioned sleeve, said sleeves havingopposed thread-like grooves formed in ther opposed faces, balls receivedin said opposed grooves, a 14,;

ing element, a driven element, a pressure plate, 156

plate toward a position to clamp said driven element to said drivingelement, means for retracting said pressure plate against the force ofsaid.

spring means including a pair of telescoping sleeves one of which isrotatable with said driving element and the other of which is bothrotatable and axially movable with respect' to the rst mentioned sleeve,said sleeves having opposed thread-like grooves formed in their opposedfaces, balls received in said opposed grooves, a retainer sleeve betweensaid sleeves embracing said balls and maintaining them in predeterminedrelation with respect to each other, a stop surface on the firstmentioned sleeve, a stop surface on said other of said sleeves, a fiangeon said retainer sleeve engageable with said stop surfaces to limit theposition of said retainer sleeve and said balls with respect to the tworst mentioned sleeves, mean: operatively connecting said other of saidsleeves with said pressure plate, and means for effecting rotation ofsaid other of said sleeves relative to the first mentioned sleeve duringrotation of said driving element.

7. In a. clutch structure, in combination, a driving element, a drivenelement, a `pressure plate, sprl'ng means constantly urging saidpressure plate toward a position to clamp saiddriven element to saiddriving element, meansfor retracting said pressure plate against theforce of said spring means including a pair of sleeve members one withinthe other and one rotatable with said driving member, opposedthread-like grooves formed in the opposed surfaces of said members,balls received in said grooves for connecting said members together, afriction member non-rotatable relative to said other member but axiallyslidable thereon, an abuttment on said other member limiting axialmovement of said friction member in one direction relative thereto,means operatively connecting said friction member and said pressureplate for interrelated movement, and a manually controllable frictionmember engageable with the first mentioned friction member. i Y.

8. In a clutch structure, in combination, a driving lelement, a drivenelement, means for connecting said elements together in drivingengagement, and means for variably controlling the establishment ofdriving engagement between said elements, comprising a member constantlydriven by the driving element, a second member movable in proportion toits movement, means constructed and arranged to be actuated by theconstantly driven member to effect movement of the second member, andmovable means for controlling the operation of the last-mentioned meansto cause the second member to move in follow-up relation to movements ofthe movable means.

9. In a clutch, in combination, a driving and a driven shaft arranged inend to end relation, friction means secured respectively to said shaftsand relatively movable for establishing variable driving connectionbetween said shafts, means constantly urging said friction means towardfull shaft connected positions, control means movable in oppositedirections between two controlling positions, power operated meansmechanically interconnected between said control means and said frictionmeans constantly driven by said driving shaft and constructed andarranged to effect relative movement between said friction means towardfull shaft connected and disconnected positions in follow-up relationwith movement of said control means between its two positions.

l0. In a clutch structure, in combination, a driving element, a drivenelement, means for securing said driving element and said driven elementtogether in 'driving engagement, and means for relieving said drivingengagement including a member constantly driven by said driving element,a member drivable by said constantly driven member to relieve saidsecuring means, and.

means movable in follow-up relation to vthe relieving movements of thedrivable member for controlling said relieving movements;

11. In a clutch structure, in combination, a driving element, a drivenelement, means for securing said driving element and said driven elementtogether in driving engagement, and means for relieving said drivingengagement including a member constantly driven by said driving element,a member bodily shiftable by said constantly driven' member to relievesaid securing means, and means movable in follow-up relation to therelieving movements of said bodily shiftable member cooperable with saidbodily shiftable member independently of said constantly driven memberfor controlling said relieving movements.

12. In combination, a driving element, a driven element frictionallyengageable therewith, means for moving one of said elements bodilyrelative to the other thereof to control said frictional engagementincluding a pair of relatively rotatable members one of which is drivenby said driving element and the other of which is cooperativelyassociated with said driven element, said members being so formed and socooperating with each other that relative rotation between them eifectsaxial movement of one with the first mentioned part, and means forcontrolling the axial position of said second'part.

13. In combination, a driving element, a driven element frictionallyassociated therewith, means for variably controlling said drivingengagement said opposed grooves, a retainer sleeve between' said sleevesembracing said balls and maintaining them in predetermined relation withrespect to each other, and means for effecting relative rotation betweensaid pair of sleeves.

ROBERT C. RUSSELL.

